During vascular surgery or endovascular treatment of vessels including thrombectomy, atherectomy, balloon angioplasty, and/or stent deployment, debris such as plaque and blood clots can move from the treatment site through a vein or artery and compromise the flow of blood at a location removed from the treatment site. In particular, various protection systems have been developed to prevent such debris from embolizing in the vessel. Distal protection devices include filters and occlusive devices (e.g., balloons) placed distally of the treatment site. Proximal protection devices include filters and occlusive devices placed proximally of the treatment site. In the case of filters, emboli collect within or on the filter. The filter with captured emboli is typically collapsed into a recovery catheter and the catheter withdrawn from the patient's body.
In prior art filters it has been found that incorrect radial position of the filter within a body conduit can compromise the performance of the filter. Specifically, if a portion of the filter abuts a vessel wall, then the area of the filter available for performing the filtering function is reduced. Further, radial motion of an elongate member can cause the filter to lose wall apposition and thereby defeat the intended embolic capture function of the filter.
Most filters are mounted onto elongate support members, and the filters are comparatively flexible as compared to the elongate support members to which they are mounted. Radial motion of the elongate support member is often a consequence of back and forth axial motion of the elongate support member in tortuous body conduits. Radial motion of the elongate support member can compress the filter, causing it to lose apposition to the conduit wall and thereby defeat the intended embolic capture function. Control of elongate member radial position by use of proximal loops is discussed in U.S. Ser. No. 09/628,212, filed Jul. 28, 2000, entitled “Improved Distal Protection Device” and U.S. Ser. No. 10/093,572, filed Mar. 8, 2002, entitled “Distal Protection Devices Having Controllable Wire Motion,” the contents of each of which are hereby incorporated by reference herein. Radial motion of the elongate support member can also press the filter against a conduit and reduce the area available for filtering emboli.
A need in the art remains for an embolic protection filter in which an elongate support member does not cause the filter to have excessive contact with a body conduit, thereby decreasing the filter area available for performing the filtering function.